VARPTR$ Malfunctions on Local Variable Length STRING Arrays (43528)

SYMPTOMS

The VARPTR$ function returns a string representation of a variable's address that can be used by the DRAW or PLAY statements. If VARPTR$ is used on an element of a local SUBprogram variable length STRING array, it generates an "Illegal Function CALL" during run time. This problem does not occur when run from within the QuickBasic environment, but only when run as a compiled program. The problem occurs when the program is compiled with or without /D, or if it is compiled as a stand-alone executable file or one requiring the run-time module.

STATUS

Microsoft has confirmed this to be a bug in Microsoft QuickBasic Versions 4.00, 4.00b, and 4.50, and the Microsoft Basic Compiler Versions 6.00 and 6.00b (buglist6.00, buglist6.00b). We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

Workarounds to this problem follow in the "More Information" section.

MORE INFORMATION

If the following program is compiled and then executed, it will generate an "Illegal Function CALL" when VARPTR$ is CALLed:

DECLARE SUB Drawit()
SCREEN 9
Drawit
END

SUB Drawit
DIM A$(10)
A$(1) = "U100L100D100R100"     'commands to draw a box
DRAW "X" + VARPTR$(A$(1))
END SUB

There are several easy workarounds for this problem:

Do not use the VARPTR$ function. The following two statements will execute identically, and the second is much easier to implement:
```
      DRAW "X" + VARPTR$(A$(1))
      DRAW A$(1)
						
```
Move the DIM statement to the Module level (main) code and change it to DIM SHARED A$(10).
Assign a temporary variable to A$(1) and use the temporary variable in the VARPTR$ function.